


Felix's Determination

by SiesFics



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Double Penetration, Felix has a fat ass, Fluffy, Glenn is supportive but also worried, Hilda is exasperated, Human Felix, M/M, Possessive Felix, Possessive Sylvain, Pouty Sylvain, Shark Sylvain, Size Difference, a grumpy human in love with his fish boyfriend, background Hilda/Dedue, background glenn/holst, belly bulge, cock drunk Felix, possessive bites, soft
Language: English
Status: Completed
Published: 2020-05-27
Updated: 2020-05-27
Packaged: 2021-03-02 18:54:43
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, No Archive Warnings Apply
Chapters: 1
Words: 6,614
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24401653
Author URL: https://archiveofourown.org/users/SiesFics/pseuds/SiesFics
Summary: Sharks are possessive by nature and Sylvain is no different. Felix belongs to him from his body to his soul, every piece of him Sylvain will hoard close to his heart. What he doesn't consider is Felix feels much the same about him, and he's determined to prove it. To Sylvain, and himself.
Relationships: Felix Hugo Fraldarius/Sylvain Jose Gautier
Comments: 4
Kudos: 105





	Felix's Determination

It wasn’t every day that someone happened to meet a merman and fall in love with them, but Felix never was like most people and given how his last year had been, he didn’t want to be. 

He tugged the curtain open to stare out at the ocean, wrinkling his nose at the sight of the ocean, lacking that familiar red hair he often saw poking out. Sylvain wasn’t awake yet, or, hadn’t reached the beach.

“Felix, stop staring and eat your breakfast.” Felix glared at his older brother and reluctantly turned away, for now. It had been his intention to hide his relationship with Sylvain from Glenn simply because it seemed like far too much trouble to explain. Glenn had found out anyway, unfortunately, by finding Felix with a giant shark man dick inside of him. He would never live it down, and Glenn was never one to forget. Despite how shocked Glenn had been, he had supported Felix, loved him, as he always had. He was concerned but he was just happy that Felix was happy, and that Felix actually went outside now. “Are you not going to see him today?” Glenn asked, cutting into the pancakes he’d whipped up for them. 

“Not until later. Hilda texted me last night and wants me to go shopping with her and since I owe her, I’m going.” He needed to go to the beach first to tell Sylvain, so as not to worry the other. He’d made the mistake once of not specifying time and Sylvain hadn’t let him go all night, and Glenn had been worried sick when he came home in the early morning, cold, wet and debauched.

He and Sylvain were in the beginnings of their relationship, only a few months in from what had been a carefully woven friendship. But Felix had been unsatisfied with just friends, and as it turned out, Sylvain had felt the same. He was glad they had ended up here, but Felix sometimes worried. Worried about if he was good enough for Sylvain, sexy enough and it pissed him off he worried about it at all. He couldn’t even take both of Sylvain’s dicks, or rather, Sylvain hadn’t let him try. Felix glared at his pancakes as he mulled over his own insecurities. 

“Ah. Well, you look to be in a lovely mood for that.” Glenn laughed and dodged the cloth napkin launched at him. “It’s nice that you’re going to spend time with your friend, you know, the one you grew up with.” 

“Shut up. You just want alone time with Holst.” Felix glared at Glenn, but it wasn’t anger, or even annoyance really. Felix was perpetually grumpy, only ever placated by his boyfriend.

“Can’t deny that. Still, you should try and have some fun.” Glenn grabbed his empty plate and set it in the sink. He ruffled Felix’s shoulder length blue-black hair and smiled when his baby brother slapped his hand away. “Have a good day Felix, love you.”

Felix huffed and looked after Glenn. “You too, love you too…” Felix wasn’t the best at showing all his emotions but he could express it easily enough with Glenn, Hilda and Sylvain. Glenn was his guardian after all, having taken care of both of them consistently for ten years. Their father travelled a lot for work so they rarely saw him and since Felix was 8 and Glenn 13, they had mostly been on their own. So Felix was damned if he didn’t show his brother some affection, even if it was few and far between. 

Felix finished his own breakfast and washed the dishes, staring out the window all the while. Their house faced the ocean and in the back a path that led to a secluded beach with a dock that made perfect meet ups for them. Felix couldn’t help but smile when from his spot in the kitchen, he looked down and saw that familiar mop of red hair poking out of the ocean, slitted golden eyes searching for him. 

Sylvain was...big. Felix exhaled and turned the water off, looking out and watching the shark swim around. Big was an understatement, he was fucking massive, his chest was bigger than most of Felix’s whole body. One hand could wrap around his entire waist, and it was stupid hot, how when Sylvain would bite at him it was all sharp teeth, so easily able to shred him.

One thing that Felix didn’t like to see on Sylvain were all the scars that littered his chest, stomach and tail from centuries of survival. Sylvain wouldn’t tell him how old he was, saying he didn’t want to seem like a creep for being with Felix, but Felix had a feeling Sylvain forgot exactly how old he was. Sometimes he would tell Felix about how he got a scar here and there, but for the most part he simply didn’t retain that information. Felix wanted to bring Sylvain out of the ocean, he’d like to sleep in a bed together, do stupid couple things that at one point made Felix gag but was now all he wanted.

He sighed and dried his hands before heading into his room to change. Felix left the house in capri shorts and a tank top, slipping on sandals as he stepped out. He hurried down the steps, weaving through the path that led to the hidden beach. 

Sylvain was blowing bubbles when he saw the familiar dark hair of his sweet little human. “Fe!” He grinned, all sharp teeth, as he swam to the dock to meet him. He wanted to pull Felix to him, hug him, and claim him. Felix was his and Sylvain had to bite and claw him every time they came together to reinstate who Felix belonged to. But before he could grab hold of his small lover, Felix stuck out a finger to stop him. Sylvain’s nose crinkled, eyes narrowing. 

“Syl, I can’t stay right now but I needed to tell you so you wouldn’t worry.” Felix knelt down on the edge of the dock, Sylvain coming up out of the water, water dripping off scarred tanned skin and that fiery hair Felix loved to pull. “Hilda wants me to shop with her, but I can’t imagine it’ll take longer than a few hours.” He sighed at Sylvain’s scowl, shaking his head. Sylvain was impossibly jealous, especially of Hilda, despite how many times Felix had assured him that they were basically family. “Sylvain, don’t pout,” he grumbled. 

“You’re leaving me!” Sylvain could just grab Felix and steal him away, but he didn’t want Felix to be angry with him. “You’ll return later? Promise?” It was rare Sylvain ever looked vulnerable, but right now he had his golden eyes widened and his lip stuck out in a pout. 

“Of course I’m coming back, stupid shark…” Felix reached out and cupped Sylvain’s large face in his small hands and in moments like these their difference in size was most obvious. Felix reached further and stroked Sylvain’s fin like ears, the merman purring and chest rumbling. He had long since discovered that his ears were especially sensitive and always served to calm him down or arouse him depending on the situation. Felix leaned in and gave Sylvain a gentle peck, pulling away before the other could draw him in anymore. Sometimes he thought Sylvain was more of a siren than anything. “I’ll be back, I love you,” he murmured, blushing and turning away. 

“Love you Fe,” Sylvain called back. He sighed and dove into the ocean, already missing Felix immensely. He was completely committed to the human. He had always been possessive, but with Felix he felt it even more, a primal urge to claim and keep him hidden from the world. 

\------

“You’re doing it again.”

“Doing what?”

“Felix!” Hilda groaned, shoulders slumping in frustration. As much as she adored Felix, who never complained whenever she asked him to do things she didn’t like doing, she was about to strangle him for his inability to stop thinking of shark dick for five minutes. “I need you to pay attention! I want to get a nice dress for my date with Dedue...he’s so quiet and I never know what he’s thinking! Do you think he tells Dimitri about me? Maybe I can get him to spill the beans.” 

“Hilda, I highly doubt Dedue talks about anything with Dimitri, let alone what he thinks about you.” Felix rolled his eyes. 

“What is THAT supposed to mean?” 

“That he’s a quiet and reserved person who doesn’t talk about much with anyone. I can’t understand your interest in him though, I figured you’d have gone for someone like Ferdinand, or Dimitri himself.” 

“First off, Ferdinand is sucking face with Hubert no matter how much they both deny it, and Dimitri has been dead set on Byleth since we were like six. You don’t pay attention, do you?” She wrinkled her nose and stuck her tongue out at him, clearly offended that he didn’t keep up with their small town gossip.

“Claude?”

“With Lorenz.”

“Ashe?”

“Yuri.”

“Petra?”

“Dorothea.” 

Shit, he really was behind on who had started dating who. One thing he DID know was not to ask about Edelgard, who Hilda was still bitter over post breakup. That had been a long month of consoling, ice cream and terrible movies. 

“Plus, they’d all be second choice to Dedue. I dunno, I just really like him Felix.” He could see in her eyes a warmth that hadn’t even been there with Edelgard, one that he recognized from his own experiences with Sylvain. 

“Then I suppose we better find you a good dress,” Felix said, feeling a determination in his stomach. He wanted for Hilda what he had with Sylvain. Hilda grinned at him and wrapped her arms around his waist, hugging him tight and knocking the wind out of him. Hilda was short and she always played up that she was weak and fragile, but the truth was that she happened to be one of the best at axe wielding, second only to Dedue. “Let me go! You hug like a bear.” Felix took a breath once she’d let go, pushing some hair out of his face. 

“So what do you think I should wear?” Hilda asked as they started up again, browsing some of the stores in their quiet beach town. 

“I don’t know Dedue intimately, but I know he cares about you. Anything you wear is going to be perfect, but I suppose we should stick with what matches you. Something pink.”

“Obviously,” Hilda chuckled. For all the grumbling Felix did, he was one of the best at picking out clothing for others and was often relied on by most everyone in their age range for that sort of thing. 

Felix did want to get back to Sylvain, but he also was having a good time with Hilda. What he was unaware of, was Sylvain, watching him and Hilda, standing on two legs. 

\-----

It had been maybe an hour before Sylvain had grown impatient, swimming furiously in the surrounding area of the town. He wanted to be with Felix, he wanted to meet the people Felix cared about and show all of them that Felix was his. 

While brooding, Sylvain took a breath and closed his eyes, remembering back long before he and Felix ever met, to the first person he had loved. Felix’s ancestor, Fraldarius, gentle and caring, polar opposites to the feisty human he now loved. Sylvain wrinkled his nose, remembering his voice, recalling how he had specialized in magic. He remembered moments of them running together along the shores, eating lunch among the flowered hills. How had that been possible? Sylvain was old, and those memories were painful to recall, so he had locked them away for centuries. But now they were flowing back, reminding him he had in fact been on land, that he had legs. Had it been the magic? Would it even still work all this time later? “Suppose there’s no reason not to try…” Sylvain grabbed hold of the dock and pulled himself out, hauling his tail with him onto land. It was a quick and seamless transition, from tail to legs.  
Human legs. 

“Holy shit,” he breathed, reaching out to feel along the calf, wiggling his toes. Swinging his legs behind him, Sylvain held himself up and looked down into the water. His fin like ears were gone, replaced with the cute human ears he always loved to tease on Felix. Likewise, his face frills were gone as well, and the gills that had once rested on either side of his waist were gone. He was excited with this newfound ability and silently thanked the man he had loved dearly, and still did in a way. A fond memory that he kept tucked away in his heart. But now it was Felix, everything was for Felix, about Felix. Sylvain loved Felix. 

“Mmm...I need to find shorts,” he murmured. He didn’t have to worry about clothes in the ocean, but on land he was very naked and from how Felix always acted, being naked around others was a no go. But Sylvain didn’t know where to find clothes, or how to get it without being seen. He was still massive in size, that much of him had remained the same, as had his clawed hands and shark teeth. Sylvain wrinkled his nose before slowly, carefully, making his way out of the secluded beach, staying low and hidden among the trees and bushes that lined the outer rim that separated beach from town. Thankfully it wasn’t busy on the actual beach, though there were a few people around, one whose clothes Sylvain might just be able to fit into.

“Say Dedue, why is it you wanted to come fishing?” Dimitri cast his line, sitting down to play what was the most boring aspect of fishing, waiting. 

“I wanted to catch some fish to prepare tonight for Hilda. I do not wish to purchase fish, though that is nothing against the fishermen. I want to catch and create the dish myself.” 

“Dedue that’s some feat! You must really like Hilda. I feel so similarly to Byleth but...she’s our professor and I heard she fancied someone already,” he sighed. 

Dedue raised a brow. “My lord, if I may be so bold as to say that I believe the person she fancies is you.”

Sylvain took the opportunity when the blond started to freak out, rushing out and grabbing the pair of shorts, and a spray bottle before running back into the bushes. More memories were returning to him about this form that had been gifted to him, and one thing he remembered was being told that while he could breathe and walk now, he had to continuously keep himself moist because the ocean was his natural home. He took a moment to spritz himself before slipping into the short. They were a bit tight, hugging his body, but not so tight his cock was outlined, though he wanted to try that when it was just him and Felix sometime. Sticking the spray bottle into the loose pocket, Sylvain headed into town. This quiet place that housed three separate major families, all heads of their households with others who followed under him. That’s how it had been when he met Fraldarius, and so it had remained. 

Strolling into town he was glad that no one stared long enough to notice how different he was. Much too tall and wide, eyes golden and slit like a snake, claws still sharp and ready to rend flesh from bone. He didn’t pay anyone much mind, sniffing the air and following the honey warm smell of Felix. He stopped short when he saw him, smiling with the girl he knew as Hilda. They’d met once and she had asked him all sorts of questions, and they had shook on their mutual care for Felix. He respected her strong desire to protect her friends, and felt her when it came to wanting to do nothing but laze around. He had done that for far too long before meeting Felix. 

\-----  
“Holy shit.” Hilda gasped, dropping the dress she’d grabbed from a rack. Felix raised a bro at her, wiggling in her strong grip that grabbed his chin and pushed his head to the side. 

“Hilda what are you-Sylvain?!” Felix’s jaw dropped and his cheeks went red when standing before him was his boyfriend, who had legs and was somehow here? He stammered, unable to form a coherent sentence and allowed Sylvain to take his hand and lead him away. 

“Bring him back in ten minutes!” Hilda shouted. 

Sylvain brought Felix to a secluded area of the town, settling them between some trees. Reluctantly he let go of Felix’s tiny hand in his, wanting to engulf this small human in his arms. 

“H-How are you here?” Felix stammered, shaking his head. 

“I remembered something from long ago, magic that let me walk on land. It’s kind of permanent? I have to constantly make sure I’m hydrated because I’m still a creature of the sea. But It’s nice, isn’t it? I wanted to spend more time with you and not force you into the ocean all the time, and now I can!” He grinned, showing all pointy teeth, delighting in the way Felix shifted, breath hitching ever so slightly. Felix was a sight to behold, all long limbs and soft body, with a fat ass that Sylvain adored burying his cock in, or his face, whichever Felix preferred. And Felix had a way with his eyes, big and cute and almost always narrowing in annoyance but on occasion they would soften. Felix was everything to Sylvain, and that’s what made this so perfect. He wouldn’t have cared to leave the ocean any other time, but Felix made him want so much more than what he had settled for. 

“It’s nice,” Felix admitted quietly. Of course it was. Having Sylvain around like this made him feel so much more happier. “Hand that over,” he said and took the bottle from Sylvain before spritzing him. “I’ll take care of this, it’ll be fun.” Like spraying a cat, except Sylvain didn’t actually seem to mind. “And where did you get those,” he asked, pointing to the shorts which he could tell weren’t a great fit. 

“Ah...I might have taken them from someone. I couldn’t just walk around naked!” 

“You stole from someone?! Sylvain, everyone knows everyone here. I’m going to have to pay them for those, no way they’ll want them back.” Felix sighed before reaching out and grabbing Sylvain’s large hand. He flushed as he held it and led them back to Hilda. He wasn’t used to displaying any form of affection in public, since before today it had always been in the ocean. 

“Finally. I thought you'd’ ditched me,” Hilda whined. “No sucking face with Felix until I’m through with him,” she said, pointing to Sylvain. “Anyway, what about this?”

It took them another few hours before Hilda finally settled on a knee length pink dress with a fluffy bottom and short sleeves. She left them almost immediately, yelling about how she was going to be late. Felix was glad he could provide company for her, but didn’t think she had anything to worry about. He had let go of Sylvain’s hand at some point, only realizing when he heard a cacophony of giggles, narrowing his eyes and turning his head.

It wasn’t a surprise Sylvain had caught the attention of women, he was attractive, tall, and he had a flirtatious nature about him that was both parts infuriating and arousing. Sylvain was smiling at the women talking to him, close mouthed and polite while they practically drooled over him. Women who thought he was single or who just didn’t care. Felix felt his stomach tie itself in knots, fists clenching. He had never been a particularly possessive person, but things were different with Sylvain. He wouldn’t give the other up to anyone, not after all they had gone through to get to this point. Felix stormed over to the flirting women and grabbed Sylvain by the arm. 

“Hey Fe!” Sylvain smiled, shocked when Felix pulled on his hair to tug him down into a kiss. Felix wasn’t one for affection, even less so in public. Sylvain wasn’t stupid though, and figured out quickly enough why his little human was so upset. Felix’s lips moved against his, possessive and claiming, wanting their audience to know who Sylvain belonged to. Sylvain broke the kiss, smoothing a hand down Felix’s smooth blue-black hair and grinning at him. The women had long since dispersed, realizing quickly enough that Sylvain wasn’t interested. “I didn’t take you for being jealous,” he teased.

Felix glared at him and grabbed his hand. “Shut up,” he growled. He brought them to the beach and down to the dock, dropping himself down and shoving his feet into the cool ocean. “I can’t believe people can be so flirtatious like that. And you were letting them!” He glared at Sylvain, who only smiled at him before sliding back into the water. 

His tail came back to him in waves, allowing him to finally feel himself again. Being on land was fun, but in the end he was a creature of the sea. Sylvain reached up and pulled Felix into the water, laughing at the protest. He moved to float on his back, Felix easily able to sit on top of him, legs dangling on either side of Sylvain’s waist. “Fe, you’re so cute when you’re jealous. But you have nothing to worry about. You’re the only person I care about, the only one who can sate my hunger.” He cupped the back of Felix’s head and pulled him down, kissing those soft lips with a passion he had reserved for Felix alone. Sylvain wasted no time, sliding his tongue into Felix’s mouth and devouring him. His little human, his pear, grabbed at his chest for purchase but could only dig his blunt nails into skin. Felix’s heartbeat was picking up and despite his attempts to keep quiet, a shaky moan escaped past his lips. Sylvain felt the fire of arousal in his belly, other arm coming around to grab hold of Felix’s waist to guide them to the shallows. 

Sylvain had carved out a small rocky area for them, breaking down the rocks with his claws until he had a nice and smooth surface. His pearl couldn’t swim, not yet, but they were working on it. Sylvain broke the kiss and pressed his forehead to Felix’s, smiling at him. 

“Y-You’re insatiable,” Felix panted, his cheeks pink from kissing and his embarrassment. 

Sylvain hummed, hands moving down until they squeezed Felix’s soft ass, appreciating how Felix was perfect, everything Sylvain wanted and more. “I am, no denying that. But so are you kitten,” he chuckled. 

“Don’t call me that!” Felix’s face managed to get even more red, but he liked it, despite himself. 

Sylvain snaked an arm around Felix’s waist and moved him onto the rock, laying him down. Felix was soaked but the day was warm and they could spend hours still out here before he needed to go home. Which was exactly what Sylvain was determined to do, to make Felix so boneless that he wouldn’t be able to walk until nightfall. “You love it, you love getting treated like this. For all the huffing you do, you sure break easily when I do this~” His body was so large it easily overtook Felix entirely, Sylvain making sure to support himself so as not to crush the small human underneath him. They’d practiced this enough that it was second nature to Sylvain, as was remarking what was his. Felix’s neck was never without bite marks at this point, a sign of his and Sylvain’s relationship, and a sign that Felix, despite his outbursts, was happy with the shark. There were times when Felix tried to mark Sylvain, but it was impossible with his harder skin, which made sense for the life he had lived but still annoyed the human. 

Sylvain latched onto Felix’s neck, making sure to only use a few teeth to worry the skin, littering nips along Felix’s neck and across his shoulder, making sure to switch sides so his pearl was adequately marked. He smirked against the bruised skin, feeling Felix wiggle underneath him but once Sylvain had him pinned it took a lot to get him to let up. 

“S-Sylvain…” Felix groaned, curling against Sylvain’s chest, feeling over the scarred flesh, craving so much more than just Sylvain’s mouth. Being with Sylvain set Felix ablaze, it destroyed what little resistance he had and made him nothing but a pile of limbs for Sylvain to do with as he pleased. He turned his head and nestled his face into Sylvain’s rust colored hair, breathing in the salty sweet smell that always filled his senses. Sylvain was careful, only marking shallowly, never biting too deep, but always covering him in so much. Now that Glenn knew, Sylvain took even less caution, to the point where he had people like Hubert asking him what had happened. “Move on, I’m not a chew toy!” Felix growled. 

Sylvain purred against the abused skin, kissing it once before finally lifting his head. “Mmm. Fe, you know sharks are possessive, and I’m no different. Still, I suppose I’ll give my kitten some attention elsewhere.” Sylvain loved teasing Felix but he wasn’t cruel, especially when Felix’s brown eyes were wide with aching want, heartbeat so quick in his chest. Sylvain could smell the arousal on him, could feel it against his belly. He slid down, settling himself between Felix’s cute legs, delicate and long, just what he wanted. Sylvain had found a perfect mate in Felix, someone he was determined to keep forever. 

“Don’t call me that!” 

Sylvain caught Felix’s ankle before the other could kick him, spreading him and diving in. Before Felix could protest, Sylvain bit the shorts and tore them right off his body, shredding the clothing without a second though. He’d catch hell for it later, but he didn’t have the patience for much else, not when his human was achingly hard underneath him. He wasted little time, long tongue running along Felix’s length, taking him in with a moan. 

Felix slapped a hand over his mouth to stifle a moan, back arching automatically at Sylvain’s touch, his mouth on him. He glared when Sylvain grabbed his wrist and pulled it away from his mouth. “Sylvain…” Felix bit his lip but couldn’t stop the shaking moan the more of him Sylvain took in his mouth. He should be going soft at the idea of his cock being in the mouth of a man with shark teeth, but if anything it made him want more. Felix’s hands curled into Sylvain’s hair and pulled hard, moaning from the vibrating groan that came from his lover. Sylvain worked him over thoroughly, tongue stroking him, mouth sucking on him until he was shaking against the rocks, hips jerking into Sylvain’s mouth, so close, so close…”Syl, I can’t...stop,” he groaned. He cursed when all that did was make Sylvain smirk and keep going, hollowing his cheeks to swallow around Felix. The younger man moaned, begging for Sylvain as he came, shooting into the redhead’s mouth, body shuddering from orgasm. He panted, resting his head against the rocks, chest heaving as he came down. 

Sylvain pulled off of his pearl, swallowing him down and licking him once more, delighted in the weak whine he got from above. He always liked making Felix cum once so he was relaxed and pliant, ready for Sylvain. His size made it so it was a necessity to prepare Felix thoroughly every time, no spur of the moment trist for them. Sylvain pressed a kiss to Felix’s quivering thigh before urging him onto his stomach. 

“Syl, I want to try something different,” Felix murmured.  
He usually heard the nickname when Felix was close to his orgasm, it wasn’t often said afterward. “What’s up Fe?” He asked, running his claws alongside Felix’s side gently, lovingly. His pearl wiggled underneath his touch, and he could feel Felix’s blush, the other was positively flustered. 

“I…” 

Sylvain leaned in, not quite having heard him. “Speak up kitten, I can’t hear you,” he purred. 

“I want to take both of you!” Felix didn’t shout, but it was much louder than what he had intended, slapping his hands over his mouth and hanging his head, letting his hair fall in front and hide him. He was naked, ass up and he was embarrassed about this? Felix felt so foolish sometimes. He waited, barely able to make out the hitch in Sylvain’s breath. He gasped quietly as Sylvain’s mouth came close to his ear, breath hot against his skin. 

“You don’t know what you do to me Fe, I love you so much. I’ll give it to you, but you’ll let me know if it’s too much, promise?” Felix nodded and Sylvain smiled, pressing a kiss to the back of his head. He was already aching himself, the sight of Felix, of tasting him and hearing his desires had Sylvain’s cocks coming out. 

Felix looked behind him, biting back a pathetic whimper at the sight of Sylvain. His boyfriend had not one, but two massive dicks, both ridged along the shafts and tapered up to pointed heads. The first time they had had sex he had only been able to take half of one of Sylvain’s dicks, but now he could easily take one. It made him want to try both. He wanted to prove to Sylvain (who wasn’t asking), as well as himself that he was the only one who was meant to be with Sylvain. No other human, or merperson could compare. 

What Sylvain was beginning to see was that his little pearl was just as possessive about him and the longer he thought about it, the more aroused he became. “Be good for me Fe, gotta get you ready for me,” murmured. Sylvain sliding back down and nestling between Felix’s perfect legs. He places his hand on Felix’s ass, running his nails along the cheeks, another mark of who Felix belonged to. He spread Felix open, dipping his head and pressing his tongue against the puckered hole. Felix twitched above, mumbling something Sylvain couldn’t quite make out. He chuckled and folded his tongue before pushing inside of him. Felix was always so tight for him, yet as they navigated their relationship he was much easier to prepare, more pliant and able to relax. His tongue was longer than a humans and he sometimes loved to just eat Felix out until he came all over himself, embarrassed and shaking. But after Felix’s confession, Sylvain didn’t want to take longer than necessary. He dove in, tongue rubbing along the inside of his little human, pressing as deep as he could get, delighting in the whimpers and moans from Felix. 

Sylvain reached out a hand and Felix fumbled to grab his back and hand his boyfriend the lube. After their first attempt, Felix always carried a bottle of lube on him and definitely hadn’t, at one point, been discovered by Hilda. He groaned when Sylvain pulled away, his fingers twitching nervously, his whole body shaking with anticipation. He did his best with his tongue, which were thicker than Felix’s fingers, but that was all they could do to prep. Sylvain’s own fingers were big enough, but Felix didn’t like the idea of getting shredded from inside with claws like the other had. It’s why Sylvain was always so fucking gentle, too much so sometimes. 

Sylvain had to take his time, he had to make sure he did this in a way that wouldn’t cause Felix harm. They went through lube quickly with how liberally Sylvain used it, but it was a necessary evil when one had two dicks. He grunted, stroking his hand over each one, aching to bury them inside of his pearl, but he had to be patient. For Felix. Though patience looked to be the last thing Felix wanted right now. He pressed the pointed tip against Felix, shuddering at the feel of being so close, waiting for Felix to nod before pushing the head in. It was a stretch in itself, Felix’s body used to this at least and accommodating him perfectly. Sylvain groaned, wanting so badly to thrust in but holding himself. They’d have to do this when he had legs sometime, so he could take Felix in places he knew would make the younger man embarrassed. 

Felix always liked this part the least, wanting to be able to just fuck Sylvain’s dicks without worry. But that’s not how it was, and he knew Sylvain would never let him hurt himself like that. He nodded for it to continue, shuddering as a few more inches pushed in, already feeling that familiar fullness inside. “Just do it Syl, you’re not gonna break me!” He huffed, wiggling his ass and trying uselessly to do it himself. Sylvain’s hands on his hips kept him locked in place and he shot a glare back at the merman. 

“Fe, you’re going to kill me,” Sylvain breathed. He knew one wouldn’t hurt Felix, not after all this time, but it was so tempting to just give him both right now. He would refrain. He pulled out almost all the way, chuckling at Felix’s immediate protest and grabbed both hips before snapping his hips and burying himself inside of Felix. He moaned, Felix’s warmth was so much, gripping him to the point that he had to hold himself back from finishing too early. “Fuck Fe, you really feel so good,” he murmured. 

Felix sobbed when Sylvain thrust inside of him, his whole body felt full instantly as Sylvain settled into him. He could feel the pressure in his stomach, where Sylvain always bulged ever so slightly from his size. At first he had been sort of scared, but now it was just stupid hot that he was able to fit Sylvain. In moments like these Felix couldn’t help but drop the walls he carefully kept up and had to beg, had to cry because he was so cock drunk on Sylvain that he couldn’t even think straight. “Syl, move please,” he gasped, jerking his hips back and letting out another choked sob at the head of Sylvain’s cock digging deep inside him, rubbing relentlessly against his prostate. 

Sylvain’s favorite moments were when Felix was like this, begging for him with tears in those beautiful brown eyes. He pulled out a few inches before thrusting back in, both men moaning at the warmth and pleasure that surrounded them. He let Felix adjust to him, certainly not sure when to begin with his second cock. It was resting on Felix’s ass, aching to be touched, to be engulfed in Felix. 

“Sylvain, the second one, please,” Felix pleaded, spreading his legs wider, flattening himself on the rock and groaning when he felt the press of Sylvain. 

“For Goddess’ sake Felix, you’re too much!” Sylvain couldn’t hold back with Felix’s insistence and pulled out enough to let the second head press to Felix’s rim. “You tell me if it’s too much,” he reminded the other before pushing forward gently. Felix’s body welcomed his second cock, the head pushing in with minimal resistance, Sylvain breathing heavy to keep himself from fucking the human underneath him. He had never felt something so incredible. Felix was his world. 

Felix’s mouth hung open, drool spilling out of his mouth from how stupid fucked out he was already. He let out a moan mixed shout when the second head pushed in, already feeling the burning stretch, but it wasn’t something he was giving into. “More, fuck. Syl, more!” He demanded. Arms wrapped around him and lifted him up, the near feral growl from his lover had Felix shaking. 

“You’re not a human, you’re a succubus,” Sylvain hissed. He wasn’t rough, holding Felix around the waist, his hands interlacing over Felix’s stomach and letting the human slide down on both of his cocks. He let out a loud moan at the feeling of both of his cocks being wrapped up in Felix’s tight heat, sweat dripping from his red hair from the strain, the pleasure. 

Felix’s vision cut out as he slid down onto both of Sylvain’s cock, unable to help the scream that came from him. It was one of bliss, of aching need. His head fell back on Sylvain’s shoulders, legs limp, at Sylvain’s mercy. “Syl, please, fuck me,” he sobbed, reaching back and grabbing at his forearms. 

Sylvain snarled, feeling something primal inside of him break. He jerked his hips, fucking himself inside of Felix, relishing in the choking cries that kept coming out of the bundle of nerves in his arms. His hands were clasped around Felix’s stomach, growling into Felix’s hair as he felt his own cocks inside of him, bulging against the tiny human’s body. Felix was his. His and only his. He fucked harder and faster into Felix, chasing his approaching orgasm with a ferocity that had Felix wailing, moaning and screaming for him all in one breath. 

Felix couldn’t think beyond “fuck” and “Sylvain,” and he didn’t know if he ever wanted to come back from it. He was so close and shakily moved his hand to wrap around his dick, moaning at the contact, jerking his hips up into his hand then back again onto Sylvain. It only took a few strokes before Felix was moaning Sylvain’s name and spilling over his hand and onto the rocks, orgasm taking what little sanity he had left.

Sylvain was close too, so close that he was burying his face into Felix’s neck, teeth screaming to mark. He bit down on Felix’s neck, piercing the skin superficially. It was enough to tease out Felix’s sweet blood and enough to push Sylvain over. He snarled into Felix’s skin, thrusting up and pushing Felix down, locking him against his cocks. Sylvain moaned as he came, feeling clarity return the longer he came, the more seed spilled into his pearl, marking him so thoroughly no one could take him. He nuzzled at Felix, who was a boneless, fucked out mess. Just how Sylvain liked him. He let himself rest inside of Felix for a few moments before slowly pulling out and laying Felix down. He watched his cum drip out of Felix’s puffy hole, so sensitive and raw from getting thoroughly fucked. Purring, Sylvain pressed the pad of his finger against Felix, chuckling at the weak attempt to kick him away. 

“Stop, I’m too sensitive,” Felix groaned. He couldn’t believe he’d actually taken both of Sylvain’s cocks and lived. He grumbled when Sylvain shifted him, but gladly curled against the redhead’s chest. He liked when Sylvain laid him on top of him like this, it felt comforting, it felt like where he belonged.

“Fe, you’re incredible. You took all of me so perfectly.” Sylvain kissed Felix’s temple and smiled. “I love you so much.” He couldn’t stop saying it, he was addicted to Felix and he wanted this moment of theirs to last forever.

Felix wrinkled his nose and lifted his head, pressing a kiss to Sylvain’s lips before burying his face in his chest. “I love you too,” he mumbled.

Sharks were possessive, this Sylvain knew. Now he knew humans were too, Felix especially.

**Author's Note:**

> Thanks for reading!
> 
> I'm on [Twitter!](https://twitter.com/SiesFics)


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